'use client'

import { useState, useEffect, useCallback } from 'react'
import { useTheme } from '@/lib/ThemeContext'
import { assignmentsApi, classesApi, subjectsApi, teachersApi } from '@/lib/stundenplan/api'
import type {
  TimetableAssignment, CreateTimetableAssignment,
  TimetableClass, TimetableSubject, TimetableTeacher,
} from '@/app/stundenplan/types'

const initialForm: CreateTimetableAssignment = {
  teacher_id: '',
  class_id: '',
  subject_id: '',
}

export function AssignmentsManager() {
  const { isDark } = useTheme()
  const [items, setItems] = useState<TimetableAssignment[]>([])
  const [classes, setClasses] = useState<TimetableClass[]>([])
  const [subjects, setSubjects] = useState<TimetableSubject[]>([])
  const [teachers, setTeachers] = useState<TimetableTeacher[]>([])
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)
  const [showForm, setShowForm] = useState(false)
  const [submitting, setSubmitting] = useState(false)
  const [form, setForm] = useState<CreateTimetableAssignment>(initialForm)

  const load = useCallback(async () => {
    setLoading(true); setError(null)
    try {
      const [asg, cls, sub, t] = await Promise.all([
        assignmentsApi.list(),
        classesApi.list(),
        subjectsApi.list(),
        teachersApi.list(),
      ])
      setItems(asg || [])
      setClasses(cls || [])
      setSubjects(sub || [])
      setTeachers(t || [])
    } catch (e) {
      setError(e instanceof Error ? e.message : 'Laden fehlgeschlagen')
    } finally { setLoading(false) }
  }, [])

  useEffect(() => { load() }, [load])

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault()
    setSubmitting(true); setError(null)
    try {
      await assignmentsApi.create(form)
      setForm(initialForm)
      setShowForm(false)
      await load()
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Anlegen fehlgeschlagen')
    } finally { setSubmitting(false) }
  }

  const handleDelete = async (id: string) => {
    if (!confirm('Lehrauftrag wirklich loeschen?')) return
    try {
      await assignmentsApi.remove(id)
      await load()
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Loeschen fehlgeschlagen')
    }
  }

  const cardClass = isDark ? 'bg-white/10 border-white/20 text-white' : 'bg-white/80 border-black/10 text-slate-900'
  const inputClass = isDark ? 'bg-white/10 border-white/20 text-white' : 'bg-white border-slate-300 text-slate-900'

  const prereqMissing = classes.length === 0 || subjects.length === 0 || teachers.length === 0

  return (
    <div className="space-y-4" data-testid="assignments-manager">
      <div className="flex items-center justify-between">
        <div>
          <h2 className={`text-xl font-semibold ${isDark ? 'text-white' : 'text-slate-900'}`}>
            Lehrauftraege ({items.length})
          </h2>
          <p className={`text-sm ${isDark ? 'text-white/60' : 'text-slate-500'}`}>
            Welcher Lehrer unterrichtet welches Fach in welcher Klasse.
          </p>
        </div>
        <button
          onClick={() => setShowForm(s => !s)}
          disabled={prereqMissing}
          className={`px-4 py-2 rounded-xl font-medium transition-colors disabled:opacity-50 ${isDark ? 'bg-indigo-500 hover:bg-indigo-600 text-white' : 'bg-indigo-600 hover:bg-indigo-700 text-white'}`}
        >
          {showForm ? 'Abbrechen' : '+ Neuer Lehrauftrag'}
        </button>
      </div>

      {prereqMissing && !loading && (
        <div className={`p-3 rounded-xl text-sm ${isDark ? 'bg-amber-500/10 border border-amber-500/30 text-amber-200' : 'bg-amber-50 border border-amber-200 text-amber-900'}`}>
          Zuerst Klassen, Faecher und Lehrer anlegen.
        </div>
      )}

      {error && <div className="p-3 rounded-xl bg-red-500/20 border border-red-500/40 text-red-300">{error}</div>}

      {showForm && (
        <form onSubmit={handleSubmit} className={`p-4 rounded-2xl border backdrop-blur-xl ${cardClass}`}>
          <div className="grid grid-cols-1 md:grid-cols-4 gap-3">
            <div>
              <label className="block text-sm mb-1 opacity-70">Lehrer</label>
              <select required value={form.teacher_id} onChange={e => setForm({ ...form, teacher_id: e.target.value })} className={`w-full px-3 py-2 rounded-lg border ${inputClass}`}>
                <option value="">— bitte waehlen —</option>
                {teachers.map(t => <option key={t.id} value={t.id}>{t.last_name}, {t.first_name}</option>)}
              </select>
            </div>
            <div>
              <label className="block text-sm mb-1 opacity-70">Klasse</label>
              <select required value={form.class_id} onChange={e => setForm({ ...form, class_id: e.target.value })} className={`w-full px-3 py-2 rounded-lg border ${inputClass}`}>
                <option value="">— bitte waehlen —</option>
                {classes.map(c => <option key={c.id} value={c.id}>{c.name}</option>)}
              </select>
            </div>
            <div>
              <label className="block text-sm mb-1 opacity-70">Fach</label>
              <select required value={form.subject_id} onChange={e => setForm({ ...form, subject_id: e.target.value })} className={`w-full px-3 py-2 rounded-lg border ${inputClass}`}>
                <option value="">— bitte waehlen —</option>
                {subjects.map(s => <option key={s.id} value={s.id}>{s.name}</option>)}
              </select>
            </div>
            <div className="flex items-end">
              <button type="submit" disabled={submitting} className="w-full px-4 py-2 rounded-lg bg-emerald-500 hover:bg-emerald-600 text-white font-medium disabled:opacity-50">
                {submitting ? 'Speichert...' : 'Anlegen'}
              </button>
            </div>
          </div>
        </form>
      )}

      {loading ? (
        <div className={`text-center py-8 opacity-60 ${isDark ? 'text-white' : 'text-slate-700'}`}>Laedt…</div>
      ) : items.length === 0 ? (
        <div className={`text-center py-8 opacity-60 ${isDark ? 'text-white' : 'text-slate-700'}`}>Noch keine Lehrauftraege.</div>
      ) : (
        <div className={`rounded-2xl border backdrop-blur-xl overflow-hidden ${cardClass}`}>
          <table className="w-full">
            <thead className={isDark ? 'bg-white/5' : 'bg-slate-100'}>
              <tr>
                <th className="text-left px-4 py-3 text-sm font-medium opacity-70">Lehrer</th>
                <th className="text-left px-4 py-3 text-sm font-medium opacity-70">Klasse</th>
                <th className="text-left px-4 py-3 text-sm font-medium opacity-70">Fach</th>
                <th className="px-4 py-3"></th>
              </tr>
            </thead>
            <tbody>
              {items.map(a => (
                <tr key={a.id} className={isDark ? 'border-t border-white/10' : 'border-t border-slate-200'}>
                  <td className="px-4 py-3 font-medium">{a.teacher_name || a.teacher_id.slice(0, 8) + '…'}</td>
                  <td className="px-4 py-3">{a.class_name || a.class_id.slice(0, 8) + '…'}</td>
                  <td className="px-4 py-3">{a.subject_name || a.subject_id.slice(0, 8) + '…'}</td>
                  <td className="px-4 py-3 text-right">
                    <button onClick={() => handleDelete(a.id)} className="text-red-400 hover:text-red-300 text-sm">Loeschen</button>
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </div>
  )
}
